Cushioning structure for power cylinders



Aug. Z3, i966 A. H, @R1-MAN ET AL 3,267,835

CUSHIONING STRUCTURE FOR POWER CYLINDERS /V` j :5 Sheets-Sheet 1 Filed Oct 23, 1965 Aug. 23, 1966 A, H, @R1-MAN ET AL 3,Z6?,815

CUSHIONING STRUCTURE FOR POWER CYLINDERS 5 Sheets-Sheet 2 Filed Oct. 2l, 1965 @JM/ww WML/@fw @fw/:zeg-

Aug. 23, 1966 A, H, ORTMAN ET AL 3,267,815

CUSHIONING STRUCTURE FOR POWER GYLINDERS 5 Sheets-Sheet 5 Filed Oct. 2l, 1965 .,e da @v70/mega United States Patent O s A3,267,815 Patented August 23, 1966 diana Filed Oct. 21, 1965, Ser. No. 506,432 1S Claims. (Cl. 91-26) This application is a continuation-in-part of United States Patent Application Serial No. 3101,634 iiled September 23, 19613, now abandoned.

This invention relates generally to cushioning structures for power cylinders .and more particularly, is concerned with a cushioning structure of the `type in which there is a non-metallic ring coopera-ting with the cushion nose of a piston and cavity of a cylinder to provide the desired function of cushioning the piston in its movement.

Power cylinders are in very wide use today and for the most part such cylinders are double acting. A valving system external of the cylinder permits the introduction of uid such as oil or compressed air into one side of the piston, while permitting the yother side to exhaust into the atmosphere or discharge into a portion of the system which has lower pressure. For the opposite or return movement, the valving arrangement inverts the functions of the ports so that the exhaust or low pressure side of the piston becomes the high pressure side of the piston and the latter moves in an opposite direction.

The problem with which this invention is concerned is the cushioning of the piston at the end of its stroke. In instances where the piston is permitted to complete its full stroke without being stopped .by a source external of the cylinder, the end of the cylinder will receive a great impact. This impact will occur unless the pistons movement is cushioned at the end of its stroke. It has thus become obvious that for long life of the apparatus with a decrease in wear, noise, etc., it is desirable to cushion the piston at the end of its stroke. This is normally done by capturing a portion of the uid just before the end of the stroke is completed and permitting the lluid to bleed from the captured volume by suitable means such as, for example, needle valves or other metering means.

Many cushioning .arrangements have been devised with varying results insofar as actual function is concerned. The basic structure is one having a .cavity at each end of the cylinder, a decreased diameter extension of :the piston at the dead end of the cylinder, and an enlargement of the piston rod at the live end of the cylinder. The extension and enlargement are termed cushion noses and are adapted to enter .the cavities provided at the cylinder ends. It will be appreciated that when a cushion nose enters a cavity, a portion of the fluid which is carried forward by the end face of the piston is captured in the cavity in the cylinder end, and subjected to compression if the fluid is -compressible. Unless this captured fluid is relieved, the piston will normally stop short of its complete stroke. Accordingly, the end of the chamber which is normally struck by the movement of the piston, is provided with a bleed passageway controlled by a valve, such as, for example, a needle valve. The bleed passageway terminates in communication with the exhaust port. A similar bleed or metering passageway is provided in the opposite end of the cylinder communicating between that end of the chamber and the other port.

After the piston has finished its stroke and it is desired that it be returned under power, the problem is to get the piston started in its movement in an opposite direction. Incoming fluid can apply its pressure only to that exposed portion olf the piston which it sees in the cavity until vthe cushion nose is withdrawn therefrom. This pressure may be applied only to the end of the cushion nose at the dead end and the annular exposed area of the enlargement at the live end, neither of which normally is sufcient to give any immediate response to movement of the piston. In some cases the pressure may not even apply sufficient power to move the piston against a load. Accordingly, such a structure has in the past been provided with a spring-pressed ball check valve which has unilateral action, remaining fully closed when the cushioning action is occurring, but opening as soon as fluid enters the cavity. This obviously requires a passageway in addition to the bleed passageway between the ends of the piston chamber and the ports. A typical example of this type of construction is shown in U.S. Patent No. 2,897,785, issued on August 4, 1959 to the instant applicants.

The invention herein uses a sealing ring to provide a fluid tight connection between the cushion nose and t-he cavity in which it enters, but has at least one .addi-tional function which eliminates the need for a ball check valve and a return fluid passageway. For convenience hereafter, the enlargement on the live end of the piston will also `be termed a cushion nose.

It is the primary object of the invention to provide a cushion construction which is simple and effective while being economical to manufacture and maintain.

A further object of the invention is to provide a cushioning structure in which there is provided a cavity with fluid passageways norm-ally closed by a nonmetallic ring, but capable of being opened by movement of the ring in order to enable the return of the piston during .a power stroke.

Other objects of the invention are concerned with the particular details of the cushioning structures and their operation and as well the methods of making the cushioning structures.

Other objects and advantages of the invention will become .apparent to those skilled in .the art as a description of the invention proceeds. Described hereinafter in considerable detail are three preferred embodiments of the invention shown in the drawings attached hereto from an examination of which the artisan will understand the operation of the invention.

In the drawings:

FIG. 1 is -a medium sectional view through a power cylinder having a cushioning structure which utilizes a first embodiment of the invention.

FIG. 2 is a fragmentary enlarged view of a portion of FIG. 1 showing one condition of the left hand sealing ring while FIG. 3 is a similar View but showing another condition of the ring caused by opposite movement of the piston.

FIG. 4 is a perspective view of the sealing ring with a portion broken away to show its details.

FIG. 5 is a fragmentary end-on plan view of a cylinder end cover constructed in accordance with a iirst embodiment of the invention.

FIG. 6 is `a median sectional view taken along the line 6-6 of FIG. 5 with a portion thereof being shown in elevation.

FIGS. 7 and 8 are views similar to those of FIGS. 5 and 6 respectively, but showing a second embodiment of the invention.

FIG. 9 is a median sectional view partially through a power cylinder having a cushioning structure which utilizes a third embodiment of the invention.

FIG. l0 is a fragmentary end-on plan view of a cylinder end cover constructed in accordance with a third embodiment of the invention.

FIG. ll is a fragmentary enlarged vie-w of FIG. 9 showing one condition of the right hand sealing ring.

The invention herein is characterized by the provision of sealing rings in the cushioning cavities formed at the ends of the cylinder which are of conventional construction but which serve functions additional to those of sealing. The rings are seated in annular galleries which communicate with axially extending fluid passag-eways or splines.

These splines may either be provided around the peripheries -of the -galleries or may be spaced radially outwardly from the gallery in the wall of the cylinder surrounding the gallery.

The splines of each cavity, regardless of their radial position, terminate in a common groove respectively, which groove in turn connects through a metering passageway with an outlet port under the control of a needle valve. The sealing ring is axially slidable within the ygallery and means are provided for limiting its sliding movement. The ring has a relatvely stiff forwardly extending annular nose which engages tightly upon the cushion nose as the cushion nose enters the cavity. This movement forces the ring to seat upon the bottom of its gallery, capturing fluid in the chamber end. The lluid then passes through the axial passageways and the metering passageway associated therewith until the stroke of the piston is completed. During this time the cavity is sealed from the piston chamber at its entrance therefrom. As soon as fluid is introduced into the port and pressure applied against the back of the ring, the ring slides axially along the cushion nose thereby unseating itself and providing access from the cushioning cavity to the piston chamber, thereby driving the piston in a reverse direction.

A feature of the invention is that the ring itself is of substantially identical construction as rod wiper-scraper rings available on the market and may be used Without any modification whatsoever.

Inviting attention now to FIG. 1, but for the cushioning structure, the construction of the piston is conventional. The cylinder is designated generally by the reference character 10 and comprises two blocks or cylinder end covers, one being the dead end cover 12 and the other being the so-called live end cover 14. The cylindrical sleeve 16 is keyed to the respective ends by metallic ilexible keys 1S and 2l) using a technique that is well known which involves the insertion of the keys through openings in the sleeve 16 which are not shown. The cylinder end covers have suitable grooves for the keys 1S and 20 which cooperate with similar grooves on the interior surface of the sleeve 16.

Each of the cylinder end covers has an enlarged chamber, the dead end chamber being shown at 22 and the live end chamber being shown at 24;. Access to the chambers is had by way of the ports 26 and 28 respectively, and it will be understood that fluid conduits are to be connected to these ports 26 and 28 which in turn are connected to a valving arrangement that permits the ports to be alternatively intake and exhaust ports, thereby controlling the stroke of the piston to be described.

A typical piston for a iluid power cylinder is shown at y30, and in this case the piston is made of discs 32 and 3.3, provided with the annular centering ring 34 and packing rings 35 to maintain `a iluid tight relationship with the interior of the sleeve 16. The piston 30 is mounted on the reduced diameter section 38 of the piston rod 40, and various packing members may be used to maintain independent iluid conditions on opposite sides of the piston. The piston rod 40 enters the live end 14 through a packing assembly 42 of any suitable construction, and the bushing 43 is held in place by the packing ring 44. An annular enlargement or, as it will be known, cushion nose 46 is provided between the piston 30 and the largest diameter portion of the piston rod 40. The free end of the piston rod 4t) is threaded to provide the stud 48,

and a cylindrical cushion nose 5@ is held to the opposite face of the piston 30 relative to the cushion nose 46 by means of a locking nut S2 `with suitable packing 54 interposed between the nut and the cushion nose S0 to keep the connection fluid tight.

Other packing members such as the Orings 56 and perhaps similar members in locations not shown may be used to keep the entire assembly Huid tight.

As thus far described, the cylinder 1t) is known. It may be understood that cushioning cavities are positioned at S3 and 60 to provide for the entry of cushion noses Sil and 46 respectively, thereby enabling the capture or" some fluid in the piston chamber which is designated 62. A metering passageway is provided in each cylinder end cover, the dead end passageway being designated 64 and the live end passageway being designated 66. These passageways are open at one end t-o annular wells 169 and 111, respectively, and communicate with the large chambers 22 and 24, respectively, at the opposite end. Needle valves 68 and 7@ control the communication between the wells 109, 111 and the chambers 22 and 24, re spectively. The needle valves may be manipulated by screw drivers from the exterior of the cylinder for the purpose of increasing yor decreasing the rate at which iluid is permitted to llow past the respective cushion nose to the particular chamber for slowing down movement of the piston at the end of its stroke. Annular wells 109 and 111 are merely axial extensions of, and annular enlargements of, bores 1M and 1%, respectively, as will be explained hereinafter.

In accordance with `the invention herein, an annular gallery 72 or 74 is provided in each of the cylinder end covers, these galleries being coaxial with the cushioning cavities 58 and 60 and of substantially larger diameter and opening to the piston chamber 62. The dead-end sealing ring gallery, as it will be called, is shown at '72, and the live end sealing ring gallery is shown at 74. Each gallery has a sealing ring therein, the sealing rings being desgnated 76 and 78 respectively, and although given different reference numerals, the rings are intended to be identical in construction.

One such ring is shown in FIG. 4. The rings 76 and 78 are identical in construciton to rod wiperscraper rings which are available on the market for the purpose of keeping rods and -other cylindrical members clean of dirt and debris. The rings are annular in configuration and comprise a generally rectangular portion 80, having a relatively stiff extension nose 82 terminating in a thick lip 84. Such scraper rings are available in a variety of sizes and by making a comparison between the diameters of the noses 46 and 5t?, as shown in FIG. l, and that of the scraper rings in FIG. 1, it will be obvious that when a cushion nose engages a ring, it enlarges the inner diameter thereof and hence expands the lip 82 and provides a very tight seal with the cushion nose. The diameter of the cushion noses 50 and 46 is somewhat smaller than the internal diameter of the cavities 58 and 61B respectively so that there is a 4substantial clearance around a cushion nose when it enters a cavity as best seen in FIGS. 2 and 3.

The galleries 72 and 74 have an axial depth measured from the respective faces 86 and 88 of the cylinder ends I so that the rings are capable of axial movement within their galleries. Suitable grooves 90 and 92 are cut in the galleries, adjacent the entrances thereof, to receive con` ventional split locking rings 94 and 96, respective-ly, to limit the axial movement of the sealing rings.

As noted previously, FIGS. 1-6 illust-rate a tirst embodiment of the novel cushioning structure, and FIGS. 7-8 depict a second, albeit similar, structure. The distinguishing features between these two embodiments arethe shape and manner of forming the Huid passageways or splines 98 and 98' in the end covers.

Looking now at FIGS. 5 and 7 respectively, it will 'be seen that there are a plurality of iluid passageways or splines formed about the periphery of each of the galleries in the end covers. Assuming that FIGS. 5 through l8 illustrate the live end cover 14 of the cylinder 10, the gallery 74 has the fluid passageways or splines 93 or 98 cut therein for a purpose to be described. The gallery 74 extends `axially to the right of the end of the cushioning cavity 60 so that in effect, an annular valve seat 100 is formed in the gallery. rlihe metering passageway 66 connects with the gallery through annular Well 111 as shown at the bottom of each of FIGS. 6 and 8. The splines 98 are semi-circular in configuration, while the splines 98 of the second embodiment are rectangular in configuration.

Looking now at FIGS. 2 and 3, there is illustrated the operation of the sealing ring 76 during movement of the piston to the left in FIG. 2 and to the right in FIG. 3. The rectangular portion `of the ring 76 fits tightly in the gallery '72 and the lip S2 is very tightly constricted about the cushion nose 50. As the piston moves to the left, it seizes the ring 716 and moves it axially within its gallery 72 to the left, until the base of the rectangular portion 80 tightly seats against the left hand valve seat 102 which is the equivalent `of the valve seat 100 previously described. Obviously, under this condition, the only outlet for iiuid from the lefthand end of the chamber 62 is by way of the splines 104 which are the equivalent of the splines 0S and 98', and the metering passageway 64, so that the movement of the piston 30 thereby will be cushioned. After the piston has finished its stroke, fiuid will enter the port 26 Iand the chamber 22 and will apply considerable pressure upon the annular area surrounding the cushion nose 50 at the point designated 106 in FIG. 2. Since the ring 82 is not confined on its right side, it is free to move axially relative to the cushion nose 50 along its gallery for a substantial distance until the right hand end surface 108 of the rectangular portion 80 engages the ring 90. At this point, of course, the splines 104 are fully uncovered at their lefthand ends and iiuid is free to liow through the splines into the piston chamber I62 and act upon the piston 30 t-o drive it to the right. This free iiow is shown by the arrows in FIG. 3.

The reverse occurs at the opposite end of the cylinder.

The sealing rings 76 and 78 are normally made of a relatively firm plastic, such as, solid polyurethane or a similar elastomer. The active liuid used in the cylinder may, to some extent, require the sealing rings to be made of other semirigid plastic materials for which purpose polytetrafluoroethylene, known commercially as Teon, can be used with success.

Referring now to FIGS. 5, 6, 7 and 8, these figures illustrate two methods of forming the splines. In FIGS. 7 and 8, the splines may be broached after the gallery 74 has lbeen cut in the end cover 14, but this requires some machining for the removal of burrs. In the construction of FIGS. 5 and 6, a simple method of forming the splines 98 is illustrated. Before the bore of the gallery is machined, holes are drilled centered on the periphery of what will be the gallery outer circumference. These -holes are drilled of proper depth and size. Thereafter the entire gallery 74 is machined out leaving the semicircular splines 98. In this manner no burrs are produced and a clean construction is provided.

Whereas the novel cushioning structures of FIGS. 1-6 and 7-8 performed most satisfactorily, certain considerations of an economic nature were encountered in the manufacturing process. The costs of machining -annular wells 109 and 111, as well as the costs of either removing the Iburr-s formed lby the embodiment of FIGS. 7-8 or the costs of precisely locating and drilling the centered holes of the embodiment of FIGS. 1-6, threatened to limit the profit margin of the manufacturer of these cushioning devices. However, by Virtue of the minor structural changes illustrated in the embodiment of FIGS. 9-1l, substantial manufacturing economies were realized without ysacrificing any of the excellent operational characteristics exhibited by the two previously discussed cushioning embodiments.

Referring now to FIGS. 9-11, the same numerals are used therein to identify the `same structural elements previously described in conjunction with FIGS. 1-8. For the sake of brevity, these elements and their functions are not described again. The distinguishing features of this third embodiment are the lannular grooves 111 and passageways or splines 106.

Annular groove 111', which is coaxial with gallery 74 as seen in FIGS. 9 and 11, corresponds in function to annular well 111 in end cover 14. Groove 111 communicates with chamber 24 and such communication is controlled by the adjustment of needle valve 70. When the sealing ring 78 is seated at the right hand end of its axial movement within gallery 74, the rear surface of the rectangular portion V80 of the ring abuts against valve seat 100. Annular groove 111 is sealed off at its inwardly opening side when ring 78 is fully expanded by engagement with cushion nose 46. An identical groove (not shown) is formed in the dead end cover 12 of cylinder 10.

Axially extending passageways 106', as seen in FIGS. 9-11, lead to the controlling needle valve and correspond in function to axial passageway or spline 106 seen in FIGS. 1-8. Passagew-ays 106 are spaced radially outwardly from the periphery of gallery 74 and radially inwardly of the exterior surf-ace of end covers 1'2 and 14. Passageways 106 extend axially through the wall of the end cover in a plane coaxial with `gallery 74. This location of passageways 106 is in contrast to the passagew-ays 106 which are formed on the periphery of gallery 74. Passageways 66 terminate in annular groove 111 and communicate with axially aligned metering passageway 66.

Passageways 66 may -be drilled either before or after the machining of groove 111 in the end covers 12 and 14. Either manner of fabrication is commercially feasible, although drilling after machining may raise .burrs.

It will be noted that in all of the three embodiments the ring -provides a self-centering arrangement for the blind end of `the cylinder, especially. There are thus no critical machining surfaces or compensating bushings and packings needed. Furthermore the ring is easily and economically replaceable, since it may be purchased on the open market in practically any size.

Considerable variation is capable of being made in the cushioning structure without in any way departing from the spirit or scope of the invention as defined in the appended claims.

What it is desired to secure by Letters Patent in the United States is:

.1. In a fluid power cylinder having end covers with ports for admit-ting and exhausting uid, a pist-on reciprocable `in a chamber in the cylinder and having at least one cushion nose, la cavity in one end cover to receive t-he cushion nose and capture such fluid in the chamber near the termination of the piston stroke and a metering passageway in said one cylinder head between said chamber and one of said ports, the invention herein which comprises: a gallery in the one cylinder end cover opening to said chamber and coaxial with said cavity, a coaxial valve seat formed in said gallery, an annular imperforate sealing ring of semirigid plastic material axially reciprocable in said gallery and adapted to engage said seat in 'fluid t-ight engagement, said metering passageway being connected between said gallery and the port of said one end cover, a plurality of axially arranged fluid passageways in the wall surrounding said gallery, said passage- Ways normally in communication with said cavity, said communication being blocked when said sealing ring is seated, and means for limiting axial movement of said sealing ring olf said seat, said sealing ring having a constri-cted nose extension adapted to sealingly but slidingly engage said cushion nose.

2. The structure as claimed in claim 1 in which said axially arranged iluid passageways are radially offset from the periphery of. said gallery within the wall of said end cover, and said passageways extend in a plane parallel to the longitudinal axis of said gallery.

3'. The structure as claimed in claim 1 in which said axially arranged iluid passageways are formed about the perihpery of said gallery, and said passageways extend in a plane parallel to the longitudinal axis of said gallery.

4. The structure as claimed in claim 3 in which said passageways are semicircular in shape.

`5. The structure as claimed in claim 3 in which said passageways are substantially rectangular in shape.

`6. ln a fluid power cylinder having end covers with ports for adm-ittin-g and exhausting fluid, a piston reciprocable in a chamber in the cylinder and having at least one cushion nose, a cavity in one cylinder end cover to receive the cushion nose and capture such iluid in the chamber near the termination of the piston stroke and a metering passageway in said one end cover between said chamber and one of said ports, the invention herein which comprises: a gallery in the one end cover opening to said chamber and coaxial with said cavity, said gallery comprising a cylindrical ,bore of larger diameter than said cavity, a coaxial valve seat formed in said gallery, said seat bein-g in a plane normal to the axis of said cavity and spaced inward of the entrance to said gallery while defining the entrance to said cavity, an annular, imperforate sealing ring of semirigid plastic material axially reciprocable in said gallery and adapted to engage said seat in ii-uid tight engagement, said metering passageway being conne-cted between said gallery and the port or said one end cover, a plurality of axially arranged fluid passageways in the wall surrounding said gallery, said passageways normally in communication with said cavity, said communication being blocked when said sealing ring is seated, and means for limiting axial movement of sa-id sealing ring off said seat, said sealing ring having a constricted nose extension adapted to sealingly but slidingly engage said cushion nose.

7. In a fluid power cylinder having end covers with ports for admitting and exhausting fluid, a piston reciprocable in a chamber in the cylinder and having at least one cushion nose, a cavity in one end cover to receive the cushion nose and capture such Afluid in the chamber near the termination of the piston stroke and a metering passageway in said one end cover between said chamber and one of said ports, the invention herein which comprises: a gallery in the one end cover opening to said chamber and coaxial with said cavity, a coaxial valve seat formed in said gallery, said gallery terminating in a well spaced further lfrom the entrance to said gallery than said seat, an annular imperforate seal-ing ring of semirigid plastic material axially reciprocable in said gallery and adapted to engage said seat in fluid tight engagement, said metering passageway being connected .between said gallery and the port of said one end cover, a plurality of axially arranged fluid passageways in the wall surrounding said gallery, said `fluid passageways and said metering passageway opening to sa-id well, said passageways normally in communication with said cavity, said communication being blocked when said sealing ring is seated, and means for limiting axial movement of said seal-ing ring off said seat, said sealing ring having a constricted nose extension adapted to sealingly but slidingly engage said cushion nose.

`8. vIn a fluid power cylinder having end covers with por-ts for admitting and exhausting uid, a piston reciprocaible in a chamber in the cylinder and having at least one cushion nose, a cavity in one end cover to receive the cushion nose and capture such iiuid in the chamber near the termination of the piston stroke and a metering passageway in said one end cover between said chamber and one of said p-orts, the invention herein which comprises: a gallery in the one end cover `open-ing to said chamber and coaxial with said cavity, a coaxial valve seat formed in said gallery, an annular imperforate sealing ring of semirigid plastic material axially reciprocable in said gallery and adapted to engage said seat in iluid tight engagement, said metering passageway being connected between said gallery and the port of said one end cover, a plurality of axially arranged fluid passageways in the periphery of said gallery, said passageways comprising grooves in the wall of said gallery, said passageways normally in communication with said cavity, said communication being blocked when said sealing ring is seated, and means :for limiting axial movement of said sealing ring off said seat, said sealing ring having a constricted nose extension adapted to sealingly but slidingly engage said cushion nose, said ring having an outer configuration that is of the same configuration and dimensions as the interior wall of said gallery, said grooves thereby permitting such duid to flow past said ring.

9. In a power cylinder of the character described, cushioning means comprising a piston having a cushion nose and reciprocable in the cylinder, a cylinder end cover having a port and a coaxial cavity of diameter larger than the nose communicating between the port and cylinder interior, a cylindrical bore in the end cover coaxial with the cavity and larger in diameter than the cavity and providing a shoulder between cavity and bore, a semirigid plastic ring tightly engaged b-ut axially reciprocal in the bore and having an end face adapted to seat against the shoulder and a portion of its inner diameter slightly smaller than the cushion nose, means preventing the ring from coming out of the bore, grooves in the wall of the bore to pass fluid by the ring, and a metering passageway in said end cover between the port and the bore in communication with said grooves.

it). Cushioning .means as claimed in claim 9 in which said grooves are formed about the periphery of said bore.

11. Cushioning means as claimed in claim 9 in which the bore terminates in a well and the metering passageway opens to the well.

l2. Cushioning means as claimed in claim 9 in which said grooves are formed intermediate the periphery of said bore and the exterior surface of said end cover.

13. Cushioning means as claimed in claim 9 in which the portion of the ring which is of smaller inner diameter than the cushion nose is a forward extension thereof of thin section capable of being distended by the cushion nose to tightly engage same.

14. Cushioning means as claimed in claim 9 in which the bore terminates in an annular groove of greater diameter than said bore, and the metering passageway opens to said annular groove for direct communication therebetween.

15. A cushioning structure -for a fluid power device which includes a cylinder having end covers, a piston reciprocable in the cylinder, ports in the covers to enable the application of uid pressure on alternate faces of the piston for alternate power strokes thereof, lat least one cushion nose on the piston and a cavity formed in one cover to receive the cushion nose at the terminal port of a piston stroke and communicating with a port, said cushioning structure comprising: a cylindrical gallery in said one cover larger in diameter than said cavity and the cavity entrance being spaced axially inward of said gallery, a valve seat at the entrance of the cavity and an annular well `between the seat and the outer wall surface of the gallery,ran imperforate annular sealing ring closely tted in said gallery in axially slidable engagement with said outer wall surface thereof an-d stop means preventing movement of said ring out of said gallery, a face of said ring adapted to seat in fluid tight connection against said seat when the ring is axially inward of said gallery to its maximum extent, the well being further inward of said gallery than said seat, axial grooves in said outer wail communicating with said well and permitting fluid ow past the ring, the inner diameter of the cavity being slightly smaller than the outer diameter of the cushion nose,

the ring having a forwardly extending relatively heavy lip which will distend under force of an internal diameter smaller than that of the cushion nose so that the cushion nose will tightly engage the ring when moving into the lcavity and carry the ring against the seat to capture fluid in the interior of the cylinder, a metering passageway 4from the well to the port of said one cover to relieve said captured fluid and cushion the terminal part of the piston stroke, the application of fluid pressure into said port serving to lift the ring oftr the seat by uid flow between the cavity and cushion nose, moving same relative said cushion nose and providing passage for uid from said port and cavity through said axial grooves to said cylinder to engage said piston to move the same away from said one end cover.

16. The structure as claimed in lclaim 2 in which said passageways are semicircular in shape.

17. The structure as claimed in Iclaim 2 in which said passageways are substantially rectangular in shape.

18. The structure as claimed in claim 1 in which passageways are circular in cross-section, respectively, and their axes lie generally in a cylindrical plane coaxial With said valve seat.

References Cited by the Examiner UNITED STATES PATENTS 2,897,785 8/1959 Ortman 91-26 2,911,952 11/1959 Peras 91-26 2,935,047 5/1960 Ortman 91-408 References Cited by the Applicant UNITED STATES PATENTS Re. 24,532 9/ 1958 Halladay et al.

2,493,602 1/ 1950 Sterrett. 2,704,996 3/ 1955 Peterson. 2,710,595 6/ 195 5 Peterson. 2,719,510 10/ 1955 Elder. 2,755,775 7/1956 Flick et al. 2,853,974 9/ 1958 Hewitt. 2,884,903 5/1959 Pauly. 2,973,744 3/ 1961 Hennels. 3,027,877 4/ 1962 Lansky.

MARTIN P. SCHWADRON, Primary Examiner.

P. T. COBRIN, Assistant Examiner. 

1. IN A FLUID POWER CYLINDER HAVING END COVERS WITH PORTS FOR ADMITTING AND EXHAUSTING FLUID, A PISTON RECIPROCABLE IN A CHAMBER IN THE CYLINDER AND HAVING AT LEAST ONE CUSHION NOSE, A CAVITY IN ONE END COVER TO RECEIVE THE CUSHION NOSE AND CAPTURE SUCH FLUID IN THE CHAMBER NEAR THE TERMINATION OF THE PISTON STROKE AND A METERING PASSAGEWAY IN SAID ONE CYLINDER HEAD BETWEEN SAID CHAMBER AND ONE OF SAID PORTS, THE INVENTION HEREIN WHICH COMPRISES: A GALLERY IN THE ONE CYLINDER END COVER OPENING TO SAID CHAMBER AND COAXIAL WITH SAID CAVITY, A COAXIAL VALVE SEAT FORMED IN SAID GALLERY, AN ANNULAR IMPERFORATE SEALING RING OF SEMIRIGID PLASTIC MATERIAL AXIALLY RECIPROCABLE IN SAID GALLERY AND ADPATED TO ENGAGE SAID SEAT I N FLUID TIGHT ENGAGEMENT, SAID METERING PASSAGEWAY BEING CONNECTED BETWEEN SAID GALLERY AND THE PORT OF SAID ONE END COVER, A PLURALITY OF AXIALLY ARRANGED FLUID PASSAGEWAYS IN THE WALL SURROUNDING SAID GALLERY, SAID PASSAGEWAYS NORMALLY IN COMMUNICATION WITH SAID CAVITY, SAID COMMUNICATION BEING BLOCKED WHEN SAID SEALING RING IS SEATED, AND MEANS FOR LIMITING AXIAL MOVEMENT OF SAID SEALING RING OFF SAID SEAT, SAID SEALING RING HAVING A CONSTRICTED NOSE EXTENSIJON ADAPTED TO SEALINGLY BUT SLIDINGLY ENGAGE SAID CUSHION NOSE. 